This invention relates to an improved method for making an intraoclular lens with integral colored haptics. Haptics are springy, filamentary lens supports, at least two in number, located about and attached to the periphery of an intraocular lens for the purpose of centering and holding the lens in proper position in the eye. At present, there are two intraocular lens-haptic structures in common use, the monolithic lens-haptic structure and the composite lens-haptic structure. The first type is a monolithic structure in which the haptics or other analogous support means are fabricated directly from a thin annulus around the lens which is an integral part of the lens itself. A lens of this type is shown in FIGS. 1A and 1B. The second lens-haptic structure is a composite unit comprising a lens with at least two filamentary haptics attached to the lens by a fastening process. An example of this type of lens is shown in FIGS. 2A and 2B.
A disadvantage of existing monolithic lens-haptic structures is that they have uncolored haptics since the haptics are made from the same material as the lens. The uncolored, transparent haptics are difficult to see; thus, the implantation of the intraocular lens is sometimes an unnecessarily prolonged and difficult process. Also, the thin haptics occasionally break off during surgery or must be explanted subsequent to disease or trauma. Because they are highly transparent, broken haptics which must be retrieved from the eye are extremely difficult for a surgeon to see. Leaving a broken haptic in the eye could produce serious negative effects for the patient. Attempts to color the integral haptics have met with limited success since any coloring material must be biologically inert with respect to the eye, and there are few such materials. Applying a surface coloration to the integral haptics has not been successful because the colored layer may lose adherence to the haptics and peel off. A haptic is only about five thousandths of an inch thick (about 0.1 mm), so such a colored layer must be quite thin. If the colorant is a dye which permeates the haptic by diffusion, the dye material could diffuse out of the haptic into the eye, and the mechanical properties of the haptic could be undesirably altered in the coloring process. Thus, the main barrier to fabricating a monolithic lens is the difficulty in making the integral haptics visible. Jaffe, U.S. Pat. No. 4,822,358, Anis, U.S. Pat. No. 4,878,911. and Hetland, U.S. Pat. No. 4,778,463 show several of these types of integral haptic configurations without any coloration of the haptic material.
Composite lens-haptic structures have widespread use because of the availability of biocompatible colored or opaque filamentary material for the haptics. The haptic material can be colored thermoplastic or thermoset filaments, or metal wires. All of these types of haptics are easily visible to a surgeon should one become separated from the lens during the implantation process. With the separately fabricated filamentary haptics, the colorant does not diffuse into the eye from the haptics. Haptics of this type are described in Orlosky, U.S. Pat. No. 4,834,749, and in Knolle, U.S. Pat. No. 4,588,405. Another advantage of the filamentary haptic is that it is usually stronger and more resistant to damage during surgery than the haptics machined from the lens material as in monolithic lenses. Even though this second type of haptic is in widespread use, some surgeons prefer the one-piece lens with integral haptics, especially if the haptics could safely be made more visible in the eye or more resistant to damage during surgery. Manufacturers of intraocular lenses also prefer a monolithic lens-haptic structure because the manufacturing yields are thought to be better for this mode of fabrication.
Therefore, an object of this invention is to produce an improved method for making a monolithic lens-haptic structure with integral colored haptics which are visible to the surgeon implanting a lens.
Another object of this invention is to produce an improved method for making a monolithic lens-haptic structure having integral colored haptics that are as strong as the haptics in the existing one piece intraocular structures with clear haptics.
An additional object of this invention is to produce an improved method for making a monolithic lens-haptic structure with integral colored haptics in which the colorant of the haptics will not transfer from the haptics to the inner structure of the eye.
A further object of this invention is to produce an improved method for making haptics that are less likely to break either during or after the implantation process than haptics made of lens material.
Still another object of this invention is to produce an improved method for making a lens-haptic structure with integral colored haptics in an economically feasible way.